Resistance unit



Feb. 4, 1941. .1. J. CERNY RESISTANCE UNIT Filed July 12, 1959720872.22?" Jsgv/z J Cern I Patented Feb. 4 1941 UNITED J STATESRESISTANCE UNIT Joseph J.'Cerny, Berwyn, Ill., assignor to Lectrohm,Inc., Cicero, 111., a co p ration of Ill inois Application July 12,1939, Serial No. 283,960

6 Claims.

The present invention relates to resistance units and has as itsprincipal, object to improve the construction of wound resistance unitsso as to so constructed as to aid in the dissipation of heat and toprotect the resistance wire against changes in insulation which commonlyoccur where the protection for the wire is composed of a moisture l5absorbing material.

The present invention also contemplates certain improvements in themethod of manufacturing resistance units whereby a resistance wire andits terminal strips are first mounted on a 20 core piece. The entireunit is then given a coating of porcelain enamel and while wet isencased in a shell of porcelain which is in the form of a split sleeve.

The features and advantages of the present in- 25 vention will appearmore fully as the description proceeds, reference being had to theaccompanying drawing wherein a preferred form of the invention is shown.It is to be understood, however, that the drawing and description areil- 30 lustrative only, and are not to be taken as limiting theinvention except insofar as it is limited by the claims.

In the drawing, Fig. 1 isa perspective view of a resistance unitembodying my invention;

35 Fig. 2 is a sectional view on the line 2-2 of Fig. 1;

Fig. 3 is a perspective view illustrating the resistance wire andterminal strips mounted on the inner porcelain member;

40 Fig. 4 illustrates the coating operation in a somewhat diagrammaticfashion, and x Figs. 5 and 6 are perspective views showing the inner andouter porcelain units. Y

Referring now to the drawing, the present in- 45 vention is embodied ina resistance unit, adapted for use in radio receiving apparatus,television sets and other apparatus of the same general nature. Theresistance unit comprises a split sleeve ill of porcelain, the sleevebeing somewhat 50 oval in cross section, as shown, a hollow core II, aresistance wire i2 and terminal strips l3 and I4. The space around thecore ll within the sleeve I is shown as exaggerated in Fig. 2. Normallythis space is just such as to permit as ready insertion of the core Hwith the resistance wire and terminal strips thereon after they havebeen dipped in porcelain enamel. In this way it is possible tosubstantially fill the space around the resistance wire and between theporcelain core and porcelain sleeve. The resistance wire I2 is placed onthe core H by holding the core in a suitable chuck and winding the wirethereon. The core II has openings l5 and I6 extending through it andthese openings serve to circulate air down the center of the resistanceunit and i0 thus-conduct away the heat. They are also utilized inholding the core in the winding chuck. When the resistance wire i2 iswound on the core, the terminal strips i3 and H are placed around thewire at the desired intervals and are clamped in place by small clips I!and i8.- The unit shown in Fig. 3 is then ready to dip in a porcelainenamel and mount in thexsleeve 10. By, using the terminal strips I3 andH, the operator can dip all but the protruding ends of the terminalstrips in porcelain enamel and then slide the whole assembly endwiseinto a sleeve M. I The excess enamel that will hang on to the unitpractically fills the space around the core ii and the resistance unitI! within the sleeve Ill. The porcelain enamel serves to bind the sleeveand the core together. This enamel is not a very good insulator, butwith the insulation provided by the porcelain sleeve ill, the resistanceis well protected from an insulation standpoint. Units of this type havebeen coated with porcelain enamel in the past, but such a material alonehas many defects. It has a tendency in humid atmospheres, when subjectedto variations in heat, to crack with small surface cracks commonlytermed crazing. By the present invention the enamel is protectedthroughout almost the entire circumference of the sleeve of theresistance unit. The only place the porcelain" enamel is exposed isalong the slot it which is it provided in the sleeve ii) for the passageof the terminalstrips i3 and i4. Since the porcelain enamelis nothardened until after the core and resistance wire are mounted in thesleeve it,

there is, of course, no cracking or damaging. of

its surface in the assembly operation.

From the above description, it is believed that the construction andoperation of my invention will be readily apparent to those skilled inthis art. Having thus described my invention, what I claim as new anddesire to-secure by Letters Patent is:

1. A resistance unit of the character described comprising a hollowcoreof porcelain, a porcelain sleeve having a narrow longitudinal slot,said said core,

sleeve enclosinz said core, a resistance wire on said wire andprojecting through the slot in said sleeve, the space within said sleeveabout the wire said core, spaced'te 11'1"};

terminal strips and core being filled with porcelain enamel.

2. A resistance unit of the character described comprising a hollow coreof porcelain, a porcelain vsaid wire and projecting through the slot insaid sleeve, said core and resistance wire being cemented in said sleevewith porcelain enamel.

3. A resistance unit of the character described comprising a core ofporcelain, a. porcelain sleeve having a narrow longitudinal slot, saidsleeve enclosing said core; a resistance wire on said core, spacedterminal strips engaged with said wire and projecting through the slotin said sleeve, .said core and resistance wire cemerited, in said sleevewith no 1 .1 enamel, said core having a. plurality or openings extendinglengthwise therethronsh.

4. A resistance unit of the character described speced terminal stripeengaged with comprising a hollow core of porcelain, a. porcelain sleevehaving a narrow longitudinal slot, said sleeve enclosing said core,aresistance wire on said core, spaced terminal strips clamped aroundsaid wire and core and projecting through the slot in said sleeve, saidcore and resistance wire being lcemented in said sleeve with porcelainename 5. A method of making resistance units which comprises wrapping a.resistance wire about a hollow porcelain core, clamping the wire inplace by means of terminal strips, coating the wire and core withporcelain enamel and mounting them while wet with the enamel in aporcelain sleeve.

6. A resistance unit of the'charecter described comprising a flattenedlongitudinally split porcelain sleeve, a flattened longitudinallyapertured porcelain core, a. resistance wire wound on said core andterminal strips clamped to the wire, said core and resistance wire beingmounted in said sleeve and secured therein by porcelain enamel, and saidstrips projecting laterally through the slot in the sleeve.

JOSEPH J. CERNY.

